[R-390] Saturday's Line & Local Report

[rbethman]

Craig et al,

Your previous comments regarding the jumper being discovered begs the 
following mental/physical exercise.

The wiring harness itself.  You have noted the "positioning of the 
wiring harness" in two places sitting on top of mounting studs.

I might suggest looking at possible fraying of the harness, and a point 
where it "may" be causing two or more conductors to be bare and touching 
each other and/or the chassis itself.

I might say that the harness is suspect, as you have found the jumper(s) 
and components touching a jumper.

In my mind, this gives the impression that it has been fiddled with 
"after" production.

Does anyone else get this from all the posts?

It is just a bit suspicious in my mind.  Even those from St. J's don't 
have those type of issues.

Bob - N0DGN

On 1/5/2014 10:56 AM, Craig Heaton wrote:
> Good Morning Charles et All,
>
> Sometime today the IF output of both receivers are going to be checked.
> Money says I'll order some new caps and see what happens. Every year for the
> last couple of years I've spent a week or so going thru the Amelco searching
> for the loud audio cause. If it were no audio, could be easier to find. Loud
> audio, just turn down the RF gain a tweak. If the caps don't fix it, the
> boombox goes back to its operating station for another year.
>
> The AF section was checked last night again; wiring good, resistors good,
> all but two caps have been replaced (C612,C601) C601 looks like a Vitamin Q,
> C612 is a silver mica. J619 & J620; terminal resistance checked per Y2K.
>
> I'm tired of swapping modules. Where I can pick a point and check voltages,
> watch the O'scope, etc; much easier.
>
> Several times the boombox has been mentioned here on the R-390 e-mail
> reflector. C603 is the leading cause in replies. At this point, caps are
> like tubes, check them in circuit. The values of all three are good to go,
> leakage is very low according to the TO-6A.  If it should bypass all audio
> to ground, we have a suspect.
>
> This week hasn't been a total loss. The jumper touching that resistor wasn't
> found before. I might add the positioning of the wiring harness in the
> Amelco lacks a little. There are two spots where the harness sits on
> mounting studs. Have to wonder how that got past a military inspection.
>
> Regards,
> Craig
>